Technical Field
The present disclosure relates to a technology for controlling an air fuel ratio of exhaust gas flowing into a three-way catalyst arranged in an exhaust passage of an internal combustion engine.
Description of Background Art
In a first literature, there is disclosed a control apparatus in which when the temperature of cooling water is equal to or less than a reference temperature, in the case of an internal combustion engine being cold started, the air fuel ratio of a mixture is controlled to a rich air fuel ratio lower than a stoichiometric air fuel ratio in an open loop manner. In addition, in this literature, there is also disclosed a method in which in the open loop control, the air fuel ratio of the mixture is gradually changed from the rich air fuel ratio to the stoichiometric air fuel ratio, according to at least one of the rise and the time course of the temperature of the cooling water.